1. Field of the Invention
The invention relates to a vacuum processing apparatus such as, for example, a plasma processing apparatus for processing a sample with plasma, and more particularly to a vacuum processing apparatus having valves located between a plurality of chambers in which the sample is moved.
2. Description of the Related Art
A known vacuum processing apparatus of the type described above comprises an atmospheric transfer chamber where at least one of the cassettes storing samples is installed and a sample is transferred and exchanged with the cassette under atmospheric pressure; a vacuum transfer chamber of a generally polygonal planar shape, having a reduced pressure and maintained at vacuum, where a robot arm for holding and transferring a sample is placed inside; a plurality of process vessels located around the periphery thereof; and a load lock chamber or unload lock chamber connected between the atmospheric transfer chamber and the vacuum transfer chamber and having an inner pressure that can be varied or configured between a reduced pressure (vacuum) equal to that in the vacuum transfer chamber and a pressure (atmospheric pressure) equal to that in the atmospheric transfer chamber, where a sample is exchanged with the atmospheric transfer chamber under atmospheric pressure and with the vacuum transfer chamber under vacuum pressure.
In addition, a configuration including a gate and a gate valve for closing and opening the gate is located between the vacuum transfer chamber and the atmospheric transfer chamber, between the vacuum transfer chamber and the load lock chamber or unload lock chamber, or between the load lock (unload lock) chamber and the atmospheric transfer chamber. The gate partitions the connected chambers and has an opening through which a sample is transferred.
In general, a plurality of such vacuum processing apparatus are located in a user's room such as a clean room adjusted to a predetermined condition to simultaneously process a plurality of samples. To improve the overall efficiency in processing samples and the efficiency in manufacturing devices or other products obtained from the processed samples, it is important to note that many of such apparatus can be installed within a limited area of the room. Therefore, it has been required to reduce the size of the apparatus to decrease its footprint.
To solve this problem, conventionally, the size of the gate valve has been reduced to decrease the footprint of the apparatus. In this conventional art, a plurality of gates with two valves for closing/opening the gate are provided between each pair of the chambers. These valves are connected to a single shaft, which is moved vertically, as well as rotated toward each gate, so that each gate can be selectively closed with the associated valve (see, for example, Japanese Laid-Open Patent Application 2002-009125).
However, the conventional art as described above has some problems because it does not fully take the following points into consideration. The apparatus according to the conventional art described above comprises, between two gates, a first pivotally supported cradle capable of rotating toward the gates, and a second pivotally supported cradle connected to the first cradle, capable of rotating toward the gates, to the second cradle being attached a cylinder for vertically moving a shaft having two valves mounted thereon. The configuration is thus complex, and bulky in the vertical direction.
In addition, the configuration of valves for closing or opening the two gates is complex, which increases time required for maintenance and other handling operations. Moreover, the housing for containing these valves and gates requires a large size, which leads to a larger footprint of the entire processing apparatus.
Furthermore, the apparatus is more prone to vibration, by which wastes and dust are likely to occur from members contained in the housing. This leads to a problem that the wafer is prone to adhesion of foreign particles and contamination.